A useful function in propagating light signals through optical fibers is the ability to modulate or shutter the intensity of light propagating through a fiber. Conventional optical waveguides are limited by the diffraction limit of light, which is proportional to the wavelength of the light of interest. Therefore, in order to modulate, deflect, or impede propagation of light in fibers, prior proposals use scattering of light on free induced carriers, which is a weak, relatively slow effect and requires shutters with relatively large sizes (e.g., about one centimeter) to shutter off the light.
In contrast to conventional optical waveguides, plasmon waveguides are not limited by the diffraction limit of light. Plasmon waveguides have been the source of significant research in recent years. Optical components such as beam splitters, interferometers, and straight waveguides have been demonstrated using textured metallic films. Furthermore, lateral confinement of the guided mode of waveguides has been proposed using nanowires or metallic stripes at a micron scale instead of the metallic films.
In addition, plasmon waveguides using metallic nanoparticles have been proposed. These nanoparticle plasmon waveguides guide light along an array of the nanoparticles by near field coupling between the nanoparticles. Furthermore, it has been demonstrated that the electromagnetic field generated by this near field coupling may be coupled to other elements near the plasmon waveguide, such as an optical fiber.
There is a need for new methods and apparatuses that modulate light propagation in fibers using sub-micron devices.